水-空氣在板式熱交換器內的流動觀察

water-air flow visualization in the plate heat exchanger

孟繁宇(Fan-yu Meng)

指導教授 ： 楊建裕

國立中央大學/工學院/能源工程研究所/碩士(2011年)

摘要

板式熱交換器作為蒸發器時，入口處的兩相冷媒因重力作用，造成流道內冷媒分佈不均，為了降低此現象，目前多於入口處裝置入口分佈器，但分佈器的開孔方向會影響冷媒在流道內的流動分佈。
所以本研究利用染料及水-空氣進行流動觀察，找出分佈器之最佳開孔方向。從染料觀察結果可知，接近流道入出口處之流量會明顯高於遠離入出口處之流量；而在板片中間部份，不同雷諾數之流動分部皆相當均勻。
而從水-空氣流動觀察結果得知，提高空泡比及水側雷諾數都會使空氣在流道內的分佈較均勻；並且得知在空泡比 在空泡比 為0.77情況下，分佈孔的最佳 ，分佈孔的最佳 ，分佈孔的最佳 開口方向 開口方向 應為 3、4、5或 6處

關鍵字

板式熱交換器 ； 分佈不均 ； 入口分佈器 ； 流動觀察 ； 水-空氣

並列摘要

When the plate heat exchanger as the evaporator, entrance two phases refrigerant because of the action of gravity that causes refrigerant flow mal-distribution in a channel. In order to reduce this phenomenon, at present is more than install inlet port distributor in the entrance, but distributor''s opening direction will affect refrigerant flow distribution in a channel.
In this research an experimental study to visualize water with dye (single phase flow) and water-air flow (two phases flow)distribution in the plate heat exchanger that in order to find the optimum distributor''s opening direction.
From dye visualization results, the flow rate nears entrance and export ports are higher than that of in the middle of place. In the middle of plate, the flow is uniformly distributed in different Reynolds number.
From water-air flow visualization results, the flow distribution will be more uniform when void fraction and Reynolds number increase. And know that the optimum distributor''s opening direction should be 3, 4, 5or 6 in void fraction is 0.77.

並列關鍵字

water-air ； flow visualization ； inlet port distributor ； mal-distribution ； Plate heat exchanger

參考文獻

Ahmad, M., Berthoud, G. and Mercier, P, 2009, “General characteristics of two- phase flow distribution in a compact heat exchanger,” International Journal of Heat and Mass Transfer, Vol. 52, pp. 442- 450.

Asano, H. Takenaka, N. and Fujii, T., 2004, “Flow characteristics of gas- liquid two- phase flow in plate heat exchanger (Visualization and void fraction measurement by neutron radiography),” Experimental Thermal and Fluid Science, Vol. 28, pp. 223- 230.

Asano, H. Takenaka, N., Wakabayashi, T. and Fujii, T., 2005, “Visualization and void fraction distribution of downward Gas- liquid two- phase flow in a plate heat exchanger by neutron radiography,” Nuclear Instruments and Methods in Physics Research A, Vol. 542, pp. 154- 160.

Croce, G. and D’Agaro, P., 2002, “Numerical analysis of forced convection in plate and frame heat exchangers,” International Journal of Numerical Methods for Heat and Fluid Flow, Vol. 12, No.6, pp. 756- 771.

Focke, W. W. and Knibbe P. G., 1984, “Flow visualization in parallel plate ducts with corrugated walls,” CSIR Report CENG M-519.